Adopting a FIV Positive Cat into a Household with FIV Negative Cats

Dr. Laci Schaible

In an effort to help adopt out special needs patients from our shelters and rescue organizations, many cat lovers weigh the pros and cons of adopting a cat that has tested positive for FIV (feline immunodeficiency virus). While some people are informed that this is a safe and noble option, as there is a vaccine available to protect against FIV, the facts are not nearly this clear.

Vaccine Myths

There is a vaccine available that can help to prevent infection with FIV, but it is very controversial among feline practitioners. The vaccine typically involves an initial vaccine, and then boosters are administered approximately 3 weeks apart (according to the vaccine's label), followed by yearly boosters as long as the risk for exposure remains. It isn't the most effective vaccine to say the least, and FIV isn't a real risk for the majority of indoor cats, so we tend to not discuss it with our cat parents.

To say the vaccine has its problems is the understatement of the year. Most feline industry experts don't recommend it, even when an FIV (+) kitty is brought into a household with FIV (-) felines. Think about that. As with other vaccines, the FIV vaccine causes the body to produce antibodies (cells that can recognize FIV and protect the body from infection). However, current FIV tests cannot tell the difference between FIV antibodies obtained through vaccination and those obtained through natural exposure to the disease. This means that once a cat is vaccinated against FIV, there is no reliable way to tell if the cat is FIV (+) or merely FIV-vaccinated. This becomes a huge concern if a roaming cat is picked up by a shelter and subsequently tested for FIV, which is a common practice at shelters. Some shelters automatically euthanize FIV (+) cats that are picked up. You can see the concern here, not to mention the medical concern of not knowing if your cats have contracted FIV if they become sick.

The other concern is that the vaccine is marginally efficacious at best, even when it does help. There are different strains of the virus and the vaccine doesn't protect against all of them. If you are interested in the vaccine, you should first find out what strain(s) the FIV (+) cat is positive for to see if the vaccine is even mildly protective against those. Otherwise, you may wrongly believe you are protecting your cats fully against the FIV virus with this vaccine when that is not one bit true.

Finally, the vaccine is adjuvanted and adjuvants cause chronic inflammation at the injection site which can lead to vaccine-associated sarcoma formation, a type of aggressive cancer.

FIV Disease Transmission –The Good News

FIV is generally transmitted to a cat through direct contact with saliva from an infected cat. Most cats are exposed through bite wounds sustained during fights with FIV-infected cats. It is a disease of unfriendly cats so avoiding fighting and biting is the best way to prevent transmission. Separating the cats to avoid contact is the only way to be 100% sure of no transmission.

While FIV isn't very easily transmitted among cats, this doesn’t mean that unsupervised cohabitation is recommended. Keeping FIV (+) cats separate from FIV (-) cats is the only way to safely have them share a home and prevent transmission. Keeping different water bowls, food bowls, and litter boxes should help with territorial aggression. Feliway diffusers (a feline pheromone) are often helpful for reducing cats’ anxiety levels but they are not a guarantee for household peace. Some cats become more prone to aggression as they age so this is also something to further consider.

The Verdict

While the number of FIV (+) cats being euthanized in our shelters is heart breaking, adopting a cat with FIV is not something many vets will endorse unless your other cats are FIV (+) as well. Ultimately, the choice is yours and it can be done with cautious separation, but you should be fully aware of the risks.

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